Along with recent developments in information communication technology, email is explosively proliferating. Email can be transmitted/received or browsed not only by PCs but also by various kinds of terminals, and consequently mail terminals in various forms have been developed.
In particular, products that can send and receive email even at a cordless home telephone terminal have been developed. In addition, products capable of transmitting/receiving or browsing email not only at a master device but also at a cordless subsidiary device have been developed.
A facsimile terminal is also used as an information communication device. Recently, home facsimile terminals with cordless telephones are becoming popular and replacing cordless telephones. When this facsimile terminal is applied to a mail terminal, a data output function (such as a printing function) and a data input function (such as a reading function) of the facsimile terminal are added. Mail can be output or an image to be attached to mail can be input. This improves the function of the terminal.
However, the product cycle of such home information terminals is very short because the information communication technology is making very rapid progress.
Therefore, in developing an information terminal with a short cycle on such a background, the product must be efficiently launched in a short period. In order to achieve such shortened launches, the product must be one that can be used in a variety of different forms by modularizing its interval components, employing unit components, or replacing the units.
However, at such a terminal, when mail information managed by a master device is to be browsed at a cordless subsidiary device, the master device must transfer the mail information to the cordless subsidiary device divisionally in many pieces because the cordless subsidiary device has a small storage capacity. In short, data transmission is inefficient.
In transmitting data with a large capacity from the master device to the subsidiary device, the subsidiary device must be managed. More specifically, the master device must divisionally transmit data, or the subsidiary device must estimate the necessary data capacity. This requirement impedes a terminal from using unit components.
In addition, when the master device transfers mail information to the subsidiary device divisionally in many pieces, this processing increases the load on the master device and hampers processing that the master device can do alone.
Furthermore, in the master and subsidiary devices with distributed functions, when data managed by the master device is to be browsed at the subsidiary device, information browsed at the subsidiary device and that stored and managed at the master device may sometimes be different.